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Method for ⁹⁰Sr Analysis in Environmental Samples Using Thermal Ionization Mass Spectrometry with Daly Ion-Counting System

Kavasi, Norbert, Sahoo, Sarata Kumar
Analytical chemistry 2019 v.91 no.4 pp. 2964-2969
freshwater lakes, ionization, mass spectrometry, radiometry, radionuclides, reference standards, sediments, spectrometers, stable isotopes, strontium
In this work, a new ⁹⁰Sr analysis method was developed using the Isotopx Ltd., Phoenix X62 thermal ionization mass spectrometer (TIMS). Excellent ion beam sensitivity was demonstrated with the detection of 1 mBq (0.2 fg) ⁹⁰Sr on a Daly ion-counting system. The abundance sensitivity for the ⁹⁰Sr/⁸⁸Sr ratio was 2.1 × 10–¹⁰, and this could ensure measurement of 100 Bq·kg–¹ (19 fg·g–¹) ⁹⁰Sr in an environmental sample with 100 μg·g–¹ stable strontium concentration. For analytical method validation, ⁹⁰Sr was determined in two certified reference materials, for example, wild berry (IRMM-426) and freshwater lake sediment (NIST-4354), for the first time in the history of TIMS. This mass spectrometry method is faster than conventional radiometric techniques; however, interference from ⁹⁰Zr and peak tailing on the higher mass side from ⁸⁸Sr must be considered for a reliable ⁹⁰Sr determination.